<script>
    (function(psdw){
        var dpr=0 , rem=0 , scale=0;
        var htmlDOM=document.documentElement;
        dpr=window.devicePixelRatio;
        var currentWidth=htmlDOM.clientWidth;
        scale=currentWidth/psdw;
        rem=psdw/7.5;
        rem=rem*scale;
        htmlDOM.style.fontSize=rem+'px';
            htmlDOM.setAttribute('data-dpr',dpr)
    })(750)
</script>